Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$119.84	7.147%	$128.405	$128.41	$128.40	$128.40
Purchase #2	$127.70	13.443%	$144.8667	$144.87	$144.85	$144.90
Purchase #3	$24.87	13.841%	$28.3123	$28.31	$28.30	$28.30
Purchase #4	$200.41	13.333%	$227.1307	$227.13	$227.15	$227.10
Purchase #5	$213.26	4.789%	$223.473	$223.47	$223.45	$223.50
Purchase #6	$245.27	12.826%	$276.7283	$276.73	$276.75	$276.70
Purchase #7	$58.37	12.396%	$65.6055	$65.61	$65.60	$65.60
7 purchase totals =	$989.72		$1,094.5215	$1,094.53	$1,094.50	$1,094.50